This invention generally relates to catheters suitable for intravascular procedures such as percutaneous transluminal coronary angioplasty (PTCA).
PTCA is a widely used procedure for the treatment of coronary heart disease, wherein a balloon dilatation catheter is advanced into the patient's coronary artery and a relatively inelastic balloon on the distal end of the catheter is inflated within the stenotic region of the patient's artery to open up the arterial passageway and increase the blood flow through the artery.
To facilitate the advancement of the dilatation catheter into the patient's coronary artery, a guiding catheter having a preshaped distal tip is first percutaneously introduced into the cardiovascular system of a patient by the Seldinger technique through the brachial or femoral arteries. The guiding catheter is advanced within the arterial system until the preshaped distal tip of the guiding catheter is disposed within the aorta adjacent the ostium of the desired coronary artery. The guiding catheter is twisted or torqued from the proximal end, which extends out of the patient, to guide the distal tip of the guiding catheter into the ostium. The balloon dilatation catheter may then be advanced through the guiding catheter into the patient's coronary artery until the balloon on the catheter is disposed within the stenotic region of the patient's artery. The balloon is then inflated to dilatate the stenosis.
One type of dilatation catheter frequently used in PTCA procedures is an over-the-wire type balloon dilatation catheter, such as the SIMPSON ULTRA LOW PROFILE.RTM., the HARTZLER ACX.RTM., the HARTZLER ACX II.RTM., the PINKERTON 0.018.TM. or the ACS TEN.TM. balloon dilatation catheter sold by the assignee of the present invention, Advanced Cardiovascular Systems, Inc. (ACS). When using an over-the-wire dilatation catheter, a guidewire is usually inserted into an inner lumen of the catheter before it is introduced into the patient's vascular system and then both are introduced into and advanced through the guiding catheter to its distal tip which is seated within the ostium of the desired coronary artery. The guidewire is first advanced out the seated distal tip of the guiding catheter into the desired coronary artery until the distal end of the guidewire extends beyond the lesion to be dilatated. The dilatation catheter is then advanced out of the distal tip of the guiding catheter into the patient's coronary artery, over the previously advanced guidewire, until the balloon on the distal extremity of the dilatation catheter is properly positioned across the lesion to be dilatated. Once properly positioned across the stenosis, the balloon is inflated one or more times to a predetermined size with radiopaque liquid at relatively high pressures (e.g., generally 4-12 atmospheres) to dilate the stenosed region of a diseased artery. After the dilatation the balloon dilatation catheter is removed from the dilated stenosis and increased rates of blood flow will pass through the dilatated region.
One of the deficiencies noted with dilatation catheters is the difficulty in getting the catheter to track over the guidewire when making sharp turns in tortuous anatomy. The tracking characteristics of a catheter is a function of both the pushability and the flexibility of the catheter shaft. Pushability generally concerns the ability of a catheter to transmit to the distal end of the catheter an axial force applied to the proximal end of the catheter. This characteristic generally relates to the stiffness of the catheter wall or the presence or absence of stiffening elements within the catheter shaft. The greater the stiffness, the greater the pushability. The ease at which the catheter can be advanced over a convoluted guidewire positioned within the patient's artery is a function of its flexibility and particularly the flexibility of the distal extremity of the catheter.
What has been needed and heretofore unavailable is an intravascular catheter which exhibits excellent trackability with little or no loss in pushability. The present invention satisfies this and other needs.